Semiconductor epitaxial wafer, method for manufacturing same, and method for manufacturing

Abstract

The purpose of the present invention is to provide a semiconductor epitaxial wafer in which the crystallinity of an epitaxial layer is excellent. A semiconductor epitaxial wafer (100) in which an epitaxial layer (20) is formed on a surface (10A) of a semiconductor wafer (10), the semiconductor epitaxial wafer (100) being characterized in that a peak value of a hydrogen concentration distribution detected by SIMS analysis exists in a surface layer portion of the semiconductor wafer (10) on the side on which the epitaxial layer (20) is formed.

Description

[0001] This application is a divisional application. The name of the invention of the parent case is "Semiconductor epitaxial wafer and its manufacturing method and solid-state imaging element manufacturing method", the application date is May 21, 2015, and the application number is 202110533773.6. Technical Field

[0002] The present invention relates to a semiconductor epitaxial wafer and a method for manufacturing the same, and a method for manufacturing a solid-state imaging element. Background Art

[0003] Semiconductor epitaxial wafers with epitaxial layers formed on semiconductor wafers are used as device substrates for various semiconductor devices such as MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), DRAM (Dynamic Random Access Memory) memory, power transistors and back-illuminated solid-state imaging elements.

[0004] For example, back-illuminated solid-state imaging elements directly take in light from the outside into the sensor by configuring a wiring layer or the like under the sensor portion, making it possible to capture clearer images or moving images even in dark places. Therefore, in recent years, they have been widely used in digital video cameras or portable phones such as smart phones.

[0005] In recent years, as semiconductor devices have become increasingly miniaturized or high-performance, in order to improve the quality of device characteristics, it is expected that the quality of semiconductor epitaxial wafers used as device substrates will be improved. In order to further improve device characteristics, crystal quality improvement technology using oxygen precipitation heat treatment and doping technology for preventing heavy metal contamination during epitaxial growth have been developed.

[0006] For example, Patent Document 1 discloses a method for manufacturing an epitaxial wafer as follows: when an epitaxial wafer is manufactured by subjecting a silicon substrate to oxygen precipitation heat treatment and then forming an epitaxial layer, the conditions of the oxygen precipitation heat treatment are controlled to manufacture an epitaxial wafer in which the leakage current value after the formation of the epitaxial layer is less than 1.5E-10A.

[0007] In addition, regarding the gettering technology, the applicant of the present application proposed in Patent Document 2 a silicon wafer having a doping agent formed at a depth of 1 μm to 10 μm from a surface on which a device is formed and a dose of 1×10 13 / cm 2 Above 3×10 14 / cm 2 The following non-metallic ions are introduced to form a pollution protection layer.

[0008] Prior art literature Patent Literature Patent Document 1: Japanese Patent Application Publication No. 2013-197373; Patent document 2: Japanese Patent Application Publication No. 2010-287855. Summary of the invention

[0009] Problems to be solved by the invention As described in Patent Documents 1 and 2, various attempts have been made to improve the quality of semiconductor epitaxial wafers. However, before this, various attempts have been made to improve the crystallinity of surface pits (pits) and the like in the surface layer of the epitaxial layer, but the crystallinity inside the epitaxial layer has been identified as being sufficiently high, and no technology for improving the crystallinity inside the epitaxial layer itself has been proposed. As long as the crystallinity inside the epitaxial layer can be further improved, it can be expected that the device characteristics will be improved.

[0010] Solutions to Solve Problems Therefore, in view of the above-mentioned problems, an object of the present invention is to provide a semiconductor epitaxial wafer having an epitaxial layer with higher crystallinity and a method for producing the same.

[0011] The inventors of the present invention have devoted themselves to the discussion to solve the above-mentioned problems, and have focused on making the peak of the hydrogen concentration distribution exist in the surface part of the semiconductor wafer on the side where the epitaxial layer is formed in the semiconductor epitaxial wafer. Here, it is known that even if hydrogen as a light element is ion-implanted into the semiconductor wafer, the hydrogen diffuses due to the heat treatment when the epitaxial layer is formed. Therefore, it is not believed that hydrogen contributes to the improvement of the device quality of semiconductor devices made using semiconductor epitaxial wafers. In fact, even if the hydrogen concentration of a semiconductor epitaxial wafer in which hydrogen ions are implanted into a semiconductor wafer under normal conditions and then an epitaxial layer is formed on the surface of the semiconductor wafer is observed, the observed hydrogen concentration is insufficient to be detected by SIMS (Secondary Ion Mass Spectrometry), and its effect is unknown. Before this, there was no known literature on the hydrogen concentration peak and its behavior that existed in the surface part of the semiconductor wafer on the side where the epitaxial layer was formed, which exceeded the detection range according to SIMS analysis. However, the inventors' experimental results show that the crystallinity of the epitaxial layer is clearly improved in a semiconductor epitaxial wafer in which a peak of hydrogen concentration distribution exists on the surface of the semiconductor wafer on the side where the epitaxial layer is formed. Therefore, the inventors recognize that hydrogen on the surface of the semiconductor wafer helps to improve the crystallinity of the epitaxial layer, and thus complete the present invention. In addition, the inventors have developed a method for preferably manufacturing such a semiconductor epitaxial wafer.

[0012] That is, the main structure of the present invention is as follows.

[0013] The semiconductor epitaxial wafer of the present invention is a semiconductor epitaxial wafer having an epitaxial layer formed on the surface of the semiconductor wafer, characterized in that a peak of hydrogen concentration distribution detected by SIMS analysis exists in the surface portion of the semiconductor wafer on the side where the epitaxial layer is formed.

[0014] Here, it is preferable that the peak value of the hydrogen concentration distribution is located within a range of 150 nm in the thickness direction from the surface of the semiconductor wafer. In addition, it is preferable that the peak concentration of the hydrogen concentration distribution is 1.0×10 17 Atom / cm 3 above.

[0015] Here, it is preferred that the semiconductor wafer has a modified layer in which carbon is dissolved in the surface layer portion, and the half maximum width of a peak of a carbon concentration distribution in the thickness direction of the semiconductor wafer in the modified layer is 100 nm or less.

[0016] In this case, it is more preferable that the peak of the carbon concentration distribution is located within a range of 150 nm from the surface of the semiconductor wafer to a depth in the thickness direction.

[0017] Furthermore, preferably, the semiconductor wafer is a silicon wafer.

[0018] In addition, the above-mentioned method for manufacturing a semiconductor epitaxial wafer is characterized in that it comprises: a first step of irradiating the surface of the semiconductor wafer with cluster ions containing hydrogen as a structural element; and a second step of forming an epitaxial layer on the surface of the semiconductor wafer after the first step, and in the first step, the beam current value of the cluster ions is set to be greater than 50 μA.

[0019] Here, it is preferable that, in the first step, the beam current value is set to 5000 μA or less.

[0020] Furthermore, it is preferred that the cluster ion further contains carbon as a structural element.

[0021] Here, preferably, the semiconductor wafer is a silicon wafer.

[0022] Furthermore, a method for manufacturing a solid-state imaging device according to the present invention is characterized in that the solid-state imaging device is formed on any of the above-mentioned semiconductor epitaxial wafers or on an epitaxial layer of a semiconductor epitaxial wafer manufactured by any of the above-mentioned manufacturing methods.

[0023] Effects of the Invention According to the present invention, a semiconductor epitaxial wafer having an epitaxial layer with higher crystallinity can be provided because a peak of hydrogen concentration distribution detected by SIMS analysis exists in the surface portion of one side of the semiconductor wafer where the epitaxial layer is formed. In addition, the present invention can provide a method for manufacturing a semiconductor epitaxial wafer having an epitaxial layer with higher crystallinity. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic cross-sectional view for explaining a semiconductor epitaxial wafer 100 according to an embodiment of the present invention.

[0025] Figure 2 This is a schematic cross-sectional view for explaining a semiconductor epitaxial wafer 200 according to a preferred embodiment of the present invention.

[0026] Figure 3 This is a schematic cross-sectional view for explaining a method for manufacturing a semiconductor epitaxial wafer 200 according to an embodiment of the present invention.

[0027] Figure 4 (A) is a schematic diagram for explaining the irradiation mechanism when cluster ions are irradiated, and (B) is a schematic diagram for explaining the implantation mechanism when monomer ions are implanted.

[0028] Figure 5 (A) is a graph showing the concentration distribution (profile) of carbon and hydrogen in a silicon wafer after irradiation with cluster ions in Reference Example 1, (B) is a TEM cross-sectional view of the surface portion of the silicon wafer involved in Reference Example 1, and (C) is a TEM cross-sectional view of the surface portion of the silicon wafer involved in Reference Example 2.

[0029] Figure 6 Graphs showing concentration distributions after epitaxial layer formation, (A) is the carbon and hydrogen concentration distributions of the epitaxial silicon wafer involved in Example 1-1, and (B) is the hydrogen concentration distribution of the epitaxial silicon wafer involved in Comparative Example 1-1.

[0030] Figure 7 This is a graph showing the TO line strength of the epitaxial silicon wafers according to Example 1-1 and Conventional Example 1-1.

[0031] Figure 8 This is a graph showing the concentration distributions of carbon and hydrogen in the epitaxial silicon wafer according to Example 2-1.

[0032] Fig. 9 This is a graph showing the TO line strength of the epitaxial silicon wafers according to Example 2-1 and Conventional Example 2-1. DETAILED DESCRIPTION

[0033] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In principle, the same reference numerals are given to the same components, and description thereof will be omitted. Figures 1 to 3 In FIG. 1 , for the sake of simplification of the drawings, the thicknesses of the semiconductor wafer 10 , the modified layer 18 , and the epitaxial layer 20 are exaggerated and shown at a ratio different from the actual thickness.

[0034] (Semiconductor epitaxial wafer) The semiconductor epitaxial wafer 100 according to one embodiment of the present invention is as follows Figure 1 As shown in the figure, a semiconductor epitaxial wafer having an epitaxial layer 20 formed on a surface 10A of a semiconductor wafer 10 is characterized in that a peak of hydrogen concentration distribution detected by SIMS analysis exists in the surface layer portion of the semiconductor wafer 10 on the side where the epitaxial layer 20 is formed. In addition, the epitaxial layer 20 is a device layer for manufacturing semiconductor elements such as back-illuminated solid-state imaging elements. The details of each structure are described in sequence below.

[0035] As the semiconductor wafer 10, there can be mentioned a bulk single crystal wafer (bulk single crystal wafer) composed of, for example, silicon, a compound semiconductor (GaAs, GaN, SiC) and having no epitaxial layer on its surface 10A. In the case of being used for the manufacture of a back-illuminated solid-state imaging element, a bulk single crystal silicon wafer is generally used. As the silicon wafer, a wafer obtained by slicing a single crystal silicon ingot grown by the Czochralski process (CZ process) or the floating zone melting process (FZ process) by a wire saw or the like can be used. Furthermore, in order to obtain a gettering capability, a semiconductor wafer 10 to which carbon and / or nitrogen are added can also be used. Furthermore, a semiconductor wafer 10 to which an arbitrary doping of a specified concentration is added, a so-called n+ type or p+ type or an n- type or p- type substrate can also be used.

[0036] As the epitaxial layer 20, a silicon epitaxial layer can be cited, which can be formed under normal conditions. For example, source gases such as dichlorosilane and trichlorosilane are introduced into the chamber using hydrogen as a carrier gas. Although the growth temperature varies depending on the source gas used, it is possible to epitaxially grow on the semiconductor wafer 10 by the CVD method at a temperature in the range of 1000 to 1200°C. In addition, with respect to the epitaxial layer 20, it is preferred that the thickness is within the range of 1 to 15 μm. This is because, when the thickness is less than 1 μm, there is a possibility that the resistivity of the epitaxial layer 20 changes due to the outward diffusion of dopants from the semiconductor wafer 10. In addition, when the thickness exceeds 15 μm, there is a possibility that the spectral sensitivity characteristics of the solid-state imaging element are affected.

[0037] Here, the presence of a peak in the hydrogen concentration distribution detected by SIMS analysis on the surface of the semiconductor wafer 10 on the side where the epitaxial layer 20 is formed is a particularly characteristic structure of the semiconductor epitaxial wafer 100 according to the present invention. Here, in view of the current detection technology using SIMS, in this specification, 7.0×10 16 Atom / cm 3 As the detection lower limit of hydrogen concentration by SIMS. The significance of the technology using such a structure including its effects will be described below.

[0038] In the past, even if hydrogen ion implantation is performed in a semiconductor epitaxial wafer to confine hydrogen in a high concentration in the semiconductor wafer, it is not considered to contribute to the improvement of semiconductor device characteristics. This is because, under the usual hydrogen ion implantation conditions into the semiconductor wafer, hydrogen is a light element. Therefore, due to the heating during the formation of the epitaxial layer, hydrogen diffuses outward after the epitaxial layer is formed, and almost no hydrogen remains in the semiconductor wafer. In fact, even if the hydrogen concentration distribution of the semiconductor epitaxial wafer subjected to the usual hydrogen ion implantation conditions is analyzed by SIMS, the hydrogen concentration is below the detection range after the epitaxial layer is formed. According to the experimental results of the present inventors (the details of the experimental conditions will be described later in the examples), the specified conditions are met, thereby, a high concentration area of ​​hydrogen can be formed on the surface of the side of the semiconductor wafer where the epitaxial layer is formed. When the present inventors focus on the behavior of hydrogen in this case, the following facts become apparent experimentally.

[0039] Although the details will be described later in the examples, the inventors observed the difference in crystallinity between the semiconductor epitaxial wafer 100 having a peak in hydrogen concentration distribution and the semiconductor epitaxial wafer of the prior art having no peak in hydrogen concentration distribution by CL (Cathode Luminescence) method. The CL method is a method for measuring crystal defects by irradiating an electron beam to a sample and detecting the excitation light when the sample transitions from the bottom of the conduction band to the top of the valence band. Figure 7 This is a graph showing the TO line intensity in the thickness direction of the semiconductor epitaxial wafer 100 according to the present invention and the semiconductor epitaxial wafer of the prior art, where a depth of 0 μm corresponds to the surface of the epitaxial layer, and a depth of 7.8 μm corresponds to the interface between the epitaxial layer and the semiconductor wafer. In addition, the TO line refers to a spectrum unique to the Si element corresponding to the band gap of Si observed by the CL method, and the stronger the TO line intensity, the higher the crystallinity of Si.

[0040] As detailed below Figure 7As shown, in the semiconductor epitaxial wafer 100 according to the present invention, there is a peak value of TO line intensity on the side of the epitaxial layer 20 close to the semiconductor wafer 10. On the other hand, in the semiconductor epitaxial wafer of the prior art, the intensity of the TO line tends to decrease from the interface between the semiconductor wafer and the epitaxial layer toward the surface of the epitaxial layer. Furthermore, the value at the surface of the epitaxial layer (depth 0 μm) is presumed to be an abnormal value due to the influence of the surface state because it is the outermost surface. Next, the inventors of the present invention imagined the case where the semiconductor epitaxial wafer 100 is used to form a device, and observed the TO line intensity when the semiconductor epitaxial wafer 100 was subjected to a heat treatment simulating device formation. As described in detail later Fig. 9 As shown in the figure, it is experimentally clear that the epitaxial layer 20 of the semiconductor epitaxial wafer 100 according to the present invention maintains the peak value of the TO line intensity and has the same degree of TO line intensity as the epitaxial layer of the conventional semiconductor epitaxial wafer in the region other than the peak value. That is, it is found that the semiconductor epitaxial wafer 100 according to the present invention having the peak value of the hydrogen concentration distribution has the epitaxial layer 20, and the epitaxial layer 20 has a higher comprehensive crystallinity than the conventional one.

[0041] The theoretical background of this phenomenon is not yet clear, and the present invention is not bound by theory, but the present inventors believe as follows. Although the details are described later, Figure 6 shows the hydrogen concentration distribution of the semiconductor epitaxial wafer 100 after the epitaxial layer is formed, Figure 8 is a graph showing the hydrogen concentration distribution of the semiconductor epitaxial wafer 100 after further performing a heat treatment simulating device formation. Figure 6 and Figure 8 When the peak value of the hydrogen concentration is reached, the peak concentration of hydrogen is reduced by performing a heat treatment simulating the formation of a device. When the variation trend of the hydrogen concentration and the TO line strength before and after the simulated heat treatment is considered, the hydrogen present in high concentration in the surface layer of the semiconductor wafer 10 by performing a heat treatment simulating the device formation process is presumed to be an element that passivates the point defects in the epitaxial layer 20 and improves the crystallinity of the epitaxial layer 20.

[0042] As described above, the semiconductor epitaxial wafer 100 of the present embodiment has the epitaxial layer 20 having higher crystallinity. The semiconductor epitaxial wafer 100 having such an epitaxial layer 20 formed thereon can improve the device characteristics of the semiconductor device manufactured using the semiconductor epitaxial wafer 100.

[0043] Furthermore, in order to obtain the aforementioned effect, as long as there is a peak of the hydrogen concentration distribution within the range from the surface 10A of the semiconductor wafer 10 to a depth of 150nm in the thickness direction, the aforementioned effect can be obtained. Therefore, the above range can be defined as the surface portion of the semiconductor wafer in this specification. Moreover, as long as there is a peak of the hydrogen concentration distribution within the range from the surface 10A of the semiconductor wafer 10 to a depth of 100nm in the thickness direction, the aforementioned effect can be obtained more reliably. Furthermore, it is physically impossible to make the peak position of the hydrogen concentration distribution exist on the outermost surface of the wafer (depth 0nm), therefore, it exists at a depth of at least 5nm.

[0044] In order to reliably obtain the above-mentioned effects, the peak concentration of the hydrogen concentration distribution is more preferably 1.0×10 17 Atom / cm 3 Above, particularly preferably 1.0×10 18 Atom / cm 3 Although not intended to be limiting, when considering the industrial production of the semiconductor epitaxial wafer 100, the upper limit of the peak concentration of hydrogen can be set to 1.0×10 22 Atom / cm 3 .

[0045] Here, in the preferred semiconductor epitaxial wafer 200 according to the present invention, as Figure 2 As shown, the semiconductor wafer 10 has a modified layer 18 after carbon solid solution in its surface part, and the half-width (half width) of the peak of the carbon concentration distribution in the thickness direction of the semiconductor wafer 10 in the modified layer 18 is preferably less than 100nm. This is because such a modified layer 18 is a region where carbon is solid-dissolved in the intercrystalline position or replacement position of the crystal in the surface part of the semiconductor wafer and locally exists, and works as a powerful doping site. In addition, from the viewpoint of obtaining a high doping ability, it is more preferred to make the half-width less than 85nm, and as a lower limit, it can be set to 10nm. In addition, the "carbon concentration distribution in the thickness direction" in this specification means the concentration distribution in the thickness direction measured using SIMS.

[0046] Furthermore, from the viewpoint of obtaining a higher gettering ability, it is also preferable that an element other than the main material of the semiconductor wafer (silicon in the case of a silicon wafer) is further dissolved in the modified layer 18 in addition to the hydrogen and carbon already described.

[0047] Furthermore, from the viewpoint of obtaining a higher gettering ability, in the semiconductor epitaxial wafer 200, it is preferred that the peak of the carbon concentration distribution is located within the range from the surface 10A of the semiconductor wafer 10 to a depth of 150 nm in the thickness direction. In addition, the peak concentration of the carbon concentration distribution is preferably 1×1015 Atom / cm 3 More than 1×10 17 ~1×10 22 Atom / cm 3 In the range of 1×10 19 ~1×10 21 Atom / cm 3 within the range.

[0048] The thickness of the modified layer 18 is defined as a region where a concentration higher than the background is detected in the above-mentioned concentration distribution, and can be within a range of 30 to 400 nm, for example.

[0049] (Method for manufacturing semiconductor epitaxial wafer) Next, an embodiment of a method for manufacturing the semiconductor epitaxial wafer 200 of the present invention described above will be described. The method for manufacturing the semiconductor epitaxial wafer 200 of an embodiment of the present invention is characterized in that: Figure 3 As shown in FIG. 1 , a first step ( Figure 3 (A), (B)), and a second step ( Figure 3 (C) In the first step, the beam current value of the cluster ions 16 is set to 50 μA or more. Figure 3 (C) is a schematic cross-sectional view of a semiconductor epitaxial wafer 200 obtained by the manufacturing method. The details of each step will be described below in order.

[0050] First, a semiconductor wafer 10 is prepared. Next, the following steps are performed: Figure 3 The first step is to irradiate the surface 10A of the semiconductor wafer 10 with cluster ions 16 containing hydrogen as a structural element as shown in (A) and (B). Here, in order to make the peak of the hydrogen concentration distribution detected by SIMS analysis exist in the surface portion on the epitaxial layer 20 side of the semiconductor wafer 10, it is important to make the beam current value of the cluster ions 16 50μA or more in the first step. As a result of irradiating the cluster ions 16 containing hydrogen under the above current value conditions, the hydrogen contained in the structural element of the cluster ions exceeds the equilibrium concentration in the surface portion on the surface 10A (i.e., the irradiated surface) side of the semiconductor wafer 10 and locally dissolves.

[0051] In this specification, "cluster ion" means a cluster ion obtained by ionizing a cluster of atoms or molecules that are aggregated into a mass and given a positive or negative charge. A cluster is a mass of atoms or molecules that are bonded together (usually about 2 to 2000 atoms or molecules).

[0052] The difference between the solid solution behavior when cluster ion irradiation is performed on the semiconductor wafer 10 and when monomer ion implantation is performed is described below. That is, for example, when monomer ions composed of a predetermined element are implanted into a silicon wafer as a semiconductor wafer, Figure 4 As shown in (B), the monomer ions sputter the silicon atoms that constitute the silicon wafer and are implanted into a specified depth position in the silicon wafer. The implantation depth depends on the type of structural elements of the implanted ions and the acceleration voltage of the ions. In this case, the concentration distribution of the specified element in the depth direction of the silicon wafer becomes relatively wide (broad), and the existence area of ​​the implanted specified element is generally about 0.5 to 1 μm. When multiple ions are irradiated simultaneously with the same energy, the lighter the element, the deeper it is implanted, that is, it is implanted into different positions corresponding to the mass of each element, so the concentration distribution of the implanted element becomes wider. In addition, in the process of forming the epitaxial layer after ion implantation, the diffusion of the implanted element due to heat is also the reason for the widening of the concentration distribution.

[0053] Furthermore, monomer ions are usually injected at an acceleration voltage of about 150 to 2000 keV. However, each ion collides with silicon atoms at this energy, so the crystallinity of the surface layer of the silicon wafer injected with monomer ions is disordered, thereby disturbing the crystallinity of the epitaxial layer grown on the wafer surface. In addition, the greater the acceleration voltage, the greater the tendency of disorder in crystallinity.

[0054] On the other hand, in the case of implanting cluster ions into a silicon wafer, Figure 4 As shown in (A), when the cluster ions 16 are injected into the silicon wafer, the energy thereof instantly causes the temperature to be in a high temperature state of about 1350 to 1400°C, and the silicon is melted. Afterwards, the silicon is rapidly cooled, and the structural elements of the cluster ions 16 are dissolved in the silicon wafer near the surface. The concentration distribution of the structural elements in the depth direction of the silicon wafer depends on the acceleration voltage and cluster size of the cluster ions, but becomes sharper than that of the single ions, and the region where the irradiated structural elements exist is generally a region below 500nm (for example, about 50 to 400nm). In addition, compared with the single ions, the irradiated ions form clusters, so there is no channeling of the crystal lattice, and the suppression of thermal diffusion of the structural elements is also the reason why the concentration distribution becomes sharp. As a result, the precipitation region of the structural elements of the cluster ions 16 can be made local and highly concentrated.

[0055] Here, as described above, hydrogen ions are light elements, and therefore, they are easily diffused due to heat treatment when the epitaxial layer 20 is formed, and are in a tendency to be difficult to stay in the semiconductor wafer after the epitaxial layer is formed. Therefore, it is not sufficient to use cluster ion irradiation to make the hydrogen precipitation area local and high concentration. It is important to make the beam current value of the cluster ions 16 50μA or more and irradiate the hydrogen ions to the surface 10A of the semiconductor wafer 10 in a relatively short time to greatly damage the surface part in order to suppress the diffusion of hydrogen during heat treatment. By making the beam current value 50μA or more, the damage becomes larger, and even after the subsequent epitaxial layer 20 is formed, the peak of the hydrogen concentration distribution detected by SIMS analysis can be present in the surface part of the epitaxial layer 20 side of the semiconductor wafer 10. On the contrary, when the beam current value is less than 50μA, the damage to the surface part of the semiconductor wafer 10 is insufficient, and hydrogen diffuses due to the heat treatment when the epitaxial layer 20 is formed. The beam current value of the cluster ions 16 can be adjusted by changing the decomposition conditions of the raw material gas in the ion source, for example.

[0056] After the above-mentioned first step, a second step is performed to form the epitaxial layer 20 on the surface 10A of the semiconductor wafer 10. The epitaxial layer 20 in the second step is as described above.

[0057] As described above, a method for manufacturing the semiconductor epitaxial wafer 200 according to the present invention can be provided.

[0058] Furthermore, in order to ensure that the peak of the hydrogen concentration distribution detected by SIMS analysis is present more reliably at the surface of the semiconductor wafer 10 even after the epitaxial layer 20 is formed, the beam current value of the cluster ions 16 is preferably 100 μA or more, more preferably 300 μA or more.

[0059] On the other hand, if the beam current value becomes too large, there is a possibility that epitaxial defects are excessively generated in the epitaxial layer 20 , and therefore, it is preferable to make the beam current value 5000 μA or less.

[0060] The irradiation conditions of the cluster ions 16 in the present invention are described below. First, as long as the structural element of the irradiated cluster ions 16 contains hydrogen, other structural elements are not particularly limited, and carbon, boron, phosphorus, arsenic, etc. can be cited. However, from the viewpoint of obtaining a higher doping ability, it is preferred that the cluster ions 16 contain carbon as a structural element. This is because a modified layer 18 is formed as a region after carbon solid solution. The covalent radius of the carbon atoms at the lattice position is smaller than that of the silicon single crystal, and therefore, a contraction field of the silicon crystal lattice is formed, which becomes a doping site for attracting impurities between the lattices.

[0061] In addition, it is also preferred that the irradiated element contains elements other than hydrogen and carbon. In particular, it is preferred to irradiate one or more doping elements selected from the group consisting of boron, phosphorus, arsenic and antimony in addition to hydrogen and carbon. This is because the type of metal that can be efficiently doped varies depending on the type of element to be solid-dissolved, and therefore, by dissolving multiple elements, a wider range of metal contamination can be dealt with. For example, in the case of carbon, nickel (Ni) can be efficiently doped, and in the case of boron, copper (Cu) and iron (Fe) can be efficiently doped.

[0062] The ionizable compound is not particularly limited, but ethane, methane, etc. can be used as the ionizable carbon source compound, and diborane, decaborane (B 10 H 14 For example, when a gas containing a mixture of diborane and decaborane is used as the material gas, a hydrogen compound cluster containing carbon, boron and hydrogen can be generated. 6 H 12 ) as the material gas, cluster ions composed of carbon and hydrogen can be generated. As the carbon source compound, it is particularly preferred to use pyrene (C 16 H 10 ), dibenzyl(C 14 H 14 ) etc. n H m (3≤n≤16, 3≤m≤10) This is because it is easy to control a small-sized cluster ion beam.

[0063] The cluster size can be appropriately set to 2 to 100, preferably 60 or less, and more preferably 50 or less. The cluster size can be adjusted by adjusting the gas pressure of the gas ejected from the nozzle, the pressure of the vacuum container, the voltage applied to the filament during ionization, etc. In addition, the cluster size can be obtained by obtaining the cluster number distribution and obtaining the average value of the cluster number using mass spectrometry based on quadrupole high-frequency electric field or time of flight mass spectrometry.

[0064] Furthermore, regarding cluster ions, there are various clusters depending on the bonding pattern. For example, they can be generated using well-known methods described in the following documents. As methods for generating a gas cluster beam, there are (1) Japanese Patent Laid-Open No. 9-41138 and (2) Japanese Patent Laid-Open No. 4-354865. As methods for generating an ion beam, there are (1) Charged Particle Beam Engineering: Junzo Ishikawa: ISBN978-4-339-00734-3: Corona Publishing Co., Ltd., (2) Electron and Ion Beam Engineering: The Institute of Electrical Engineers of Japan: ISBN4-88686-217-9: Ohmsha, Ltd., and (3) Cluster Ion Beam: Fundamentals and Applications: ISBN4-526-05765-7: Nikkan Kogyo Shimbun, Ltd. In addition, generally, for the generation of positively charged cluster ions, a Nielsen-type ion source or a Kaufman-type ion source is used, and for the generation of negatively charged cluster ions, a high-current negative ion source using a volume production method is used.

[0065] The acceleration voltage of the cluster ions, together with the cluster size, affects the peak position of the concentration distribution in the thickness direction of the structural elements of the cluster ions. In order to make the peak of the hydrogen concentration distribution exist in the surface layer portion on the epitaxial layer side of the semiconductor wafer 10 even after the epitaxial layer is formed, the acceleration voltage of the cluster ions is more than 0 keV / cluster and less than 200 keV / cluster, preferably 100 keV / cluster or less, and more preferably 80 keV / cluster or less. Furthermore, in the adjustment of the acceleration voltage, generally, two methods, namely (1) electrostatic acceleration and (2) high-frequency acceleration, are used. As the former method, there is a method of arranging multiple electrodes at equal intervals, applying equal voltages between them, and creating a uniform acceleration electric field in the axial direction. As the latter method, there is a linear accelerator (linac) method of accelerating ions using high-frequency while making the ions pass by linearly.

[0066] In addition, the dose of the cluster ions can be adjusted by controlling the ion irradiation time. In the present embodiment, the dose of hydrogen can be made 1×10 13 ~1×10 16 atoms / cm 2 , preferably 5×10 13 atoms / cm 2 or more. This is because, when it is less than 1×10 13 atoms / cm 2 , there is a possibility of hydrogen diffusion during the formation of the epitaxial layer, and when it exceeds 1×10 16 atoms / cm 2 , there is a possibility of causing significant damage to the surface of the epitaxial layer 20.

[0067] In addition, when irradiating with cluster ions containing carbon as a structural element, the dose of carbon was set to 1×10 13 ~1×10 16 Atom / cm 2 is preferred, more preferably 5×10 13 Atom / cm 2 This is because, in less than 1×10 13 Atom / cm 2 In the case of more than 1×10 16 Atom / cm 2 In this case, there is a possibility that significant damage will be imparted to the surface of the epitaxial layer 20 .

[0068] Furthermore, it is also preferable to perform a recovery heat treatment for recovering the crystallinity of the semiconductor wafer 10 after the first step and before the second step. As the recovery heat treatment in this case, the semiconductor wafer 10 can be kept at a temperature of 900° C. to 1100° C. for a period of 10 minutes to 60 minutes in an environment such as nitrogen or argon. In addition, the recovery heat treatment can also be performed using a rapid temperature rise and fall heat treatment device such as RTA (Rapid Thermal Annealing) or RTO (Rapid Thermal Oxidation) that is separate from the epitaxial device.

[0069] In addition, the semiconductor wafer 10 can be a silicon wafer as already described.

[0070] Hereinbefore, an embodiment of a method for manufacturing a semiconductor epitaxial wafer 200 has been described in which, after the epitaxial layer 20 is formed by irradiation with cluster ions containing hydrogen, a peak of hydrogen concentration distribution detected by SIMS analysis exists in the surface layer portion of the semiconductor wafer 10 on the side where the epitaxial layer 20 is formed. However, of course, the semiconductor epitaxial wafer according to the present invention can also be manufactured by other manufacturing methods.

[0071] (Method for manufacturing solid-state imaging element) The method for manufacturing a solid-state imaging element according to an embodiment of the present invention is characterized in that the solid-state imaging element is formed on the epitaxial layer 20 located on the surface of the semiconductor epitaxial wafer or the semiconductor epitaxial wafer manufactured by the above-mentioned manufacturing method, that is, the semiconductor epitaxial wafer 100, 200. The solid-state imaging element obtained by this manufacturing method can sufficiently suppress the occurrence of white damage defects compared with the conventional ones.

[0072] Hereinafter, the present invention will be described in further detail using examples; however, the present invention is not limited to the following examples at all. Example

[0073] (Reference experimental example) First, in order to make the difference in the damage state in the surface layer of the silicon wafer due to the difference in the beam current value of the cluster ions clear, the following experiment was performed.

[0074] (Reference Example 1) A p-type silicon wafer (diameter: 300 mm, thickness: 775 μm, doping type: boron, resistivity: 20 Ω·cm) obtained from a CZ single crystal was prepared. Next, a cluster ion generator (manufactured by Nissin Ion Instruments Co., Ltd., model: CLARIS) was used to generate cyclohexane (C 6 H 12 ) After cluster ionization, C 3 H 5 The silicon wafer involved in Reference Example 1 was produced by irradiating the surface of the silicon wafer with cluster ions at an acceleration voltage of 80 keV / cluster (acceleration voltage of 1.95 keV / atom per hydrogen atom, acceleration voltage of 23.4 keV / atom per carbon atom, range distance of hydrogen of 40 nm, range distance of carbon of 80 nm). The dose when irradiating the cluster ions was converted to 1.6×10 15 Atom / cm 2 , which is converted to the number of carbon atoms is 1.0×10 15 Atom / cm 2 Furthermore, the beam current value of the cluster ion was set to 800 μA.

[0075] (Reference Example 2) A silicon wafer according to Reference Example 2 was produced under the same conditions as Reference Example 1 except that the beam current value of cluster ions was changed to 30 μA.

[0076] (Concentration distribution of silicon wafer) The silicon wafers of Reference Examples 1 and 2 after cluster ion irradiation were subjected to magnetic field type SIMS measurement to measure the distribution of hydrogen concentration and carbon concentration in the thickness direction of the wafer. Figure 5 (A) shows the concentration distribution of Reference Example 1. In Reference Example 2, where only the beam current value was changed, the same concentration distribution was obtained. Figure 5 (A) The same concentration distribution. Figure 5 The depth of the horizontal axis of (A) is set to zero on the surface of the silicon wafer on the cluster ion irradiation side.

[0077] (TEM cross-section) The cross-section of the silicon wafer surface layer including the cluster ion irradiation region of the silicon wafers according to Reference Examples 1 and 2 was observed by TEM (Transmission Electron Microscope). Figure 5 (B) and (C) show TEM cross-sectional photographs of the silicon wafers according to Reference Examples 1 and 2, respectively. Figure 5 The location where the black contrast appears in the encircled portion in (B) is an area where the damage is particularly large.

[0078] like Figure 5 As shown in (A) to (C), in reference example 1 with a beam current value of 800 μA, a particularly large damaged area is formed on the surface of the silicon wafer, but in reference example 2 with a beam current value of 30 μA, no particularly large damaged area is formed. Reference examples 1 and 2 are both considered to be examples in which, although the concentration distributions of hydrogen and carbon show the same trend due to the same dose conditions, the formation behavior of the damaged area on the surface of the silicon wafer is different due to the difference in beam current values. Figure 5 (A) and (B) It is considered that a region with particularly large damage is formed in the region between the peak position of the hydrogen concentration and the peak position of the carbon concentration.

[0079] (Experimental Example 1) (Example 1-1) Under the same conditions as in Reference Example 1, the silicon wafer was irradiated with C 3 H 5 Thereafter, the silicon wafer was transported to a single wafer processing epitaxial growth apparatus (manufactured by Applied Materials), and after a hydrogen bake treatment was performed at 1120°C for 30 seconds in the apparatus, an epitaxial layer of silicon (thickness: 7.8 μm, doping type: boron, resistivity: 10 Ω·cm) was epitaxially grown on the surface of the silicon wafer by a CVD method at 1150°C using hydrogen as a carrier gas and trichlorosilane as a source gas, thereby producing the epitaxial wafer involved in Example 1-1.

[0080] (Comparative Example 1-1) An epitaxial wafer according to Comparative Example 1-1 was produced under the same conditions as in Example 1-1 except that the beam current value of cluster ions was changed to 30 μA.

[0081] (Previous example 1-1) An epitaxial wafer according to Conventional Example 1-1 was produced under the same conditions as in Example 1-1 except that cluster ion irradiation was not performed.

[0082] (Evaluation 1-1: Concentration Distribution Evaluation of Epitaxial Wafer Using SIMS) The silicon wafers involved in Example 1-1 and Comparative Example 1-1 were subjected to magnetic field type SIMS measurement to measure the distribution of hydrogen concentration and carbon concentration in the thickness direction of the wafer. Figure 6 (A) shows the concentration distribution of hydrogen and carbon in Example 1-1. Figure 6 (B) shows the hydrogen concentration distribution of Comparative Example 1-1. Figure 6 The depth of the horizontal axis of (A) and (B) is set to zero at the epitaxial layer surface of the epitaxial wafer. The depth before 7.8 μm is equivalent to the epitaxial layer, and the depth above 7.8 μm is equivalent to the silicon wafer. In addition, when SIMS measurement is performed on the epitaxial wafer, an inevitable measurement error of about ±0.1 μm occurs in the thickness of the epitaxial layer. Therefore, 7.8 μm in the figure cannot be a boundary value between the epitaxial layer and the silicon wafer in a strict sense.

[0083] (Evaluation 1-2: TO line strength evaluation by CL method) The CL method was performed on the samples of the epitaxial wafers involved in Example 1-1, Comparative Example 1-1 and Conventional Example 1-1 after the angle grinding process in the cross-sectional direction, and the CL spectra in the thickness (depth) direction of the epitaxial layer were obtained. As the measurement conditions, the electron beam was irradiated at 20 keV at 33K. Figure 7 2 shows the measurement results of the CL strength in the thickness direction of Example 1-1 and Comparative Example 1-1. The measurement results of Comparative Example 1-1 are the same as those of Conventional Example 1-1.

[0084] If used Figure 5 (A) As described above, there is a peak value of hydrogen concentration in the surface layer of the silicon wafer after cluster ion irradiation and before the epitaxial layer is formed, regardless of the beam current value (see Reference Examples 1 and 2 of the reference experiment). Here, referring to the results of Reference Example 1 and Example 1-1 with a beam current value of 800 μA, it is known that the peak concentration of hydrogen before the epitaxial layer is formed is about 7×10 20 Atom / cm 3 , the peak concentration of hydrogen after the epitaxial layer is formed is reduced to about 2×10 18 Atom / cm 3 ( Figure 5 (A) Figure 6 (A)). On the other hand, although there is a peak concentration of hydrogen before the epitaxial layer is formed when the beam current value is 30 μA, the peak of the hydrogen concentration disappears after the epitaxial layer is formed ( Figure 6 (B)). This is believed to be because: as long as the beam current value is 800μA, the surface of the silicon wafer is severely damaged, so hydrogen will not diffuse completely and remain even through the heat treatment during epitaxial layer formation. This phenomenon is also believed to be Figure 5 (B) Hydrogen is trapped in the damaged area shown.

[0085] In addition, if Figure 7 As shown in the figure, in Example 1-1, there is a peak value of the TO line intensity at a depth of about 7 μm from the epitaxial layer surface. On the other hand, in the epitaxial wafer involved in the conventional example 1-1, the intensity of the TO line decreases from the silicon wafer interface toward the epitaxial layer surface. In addition, the value at the epitaxial layer surface (depth 0 μm) is the surface, so it is estimated that the influence of the surface state.

[0086] (Experimental Example 2) (Example 2-1) Furthermore, the epitaxial wafer simulated device formation according to Example 1-1 was subjected to heat treatment at a temperature of 1100° C. for 30 minutes.

[0087] (Previous example 2-1) The epitaxial wafer according to Conventional Example 1-1 was subjected to heat treatment at 1100° C. for 30 minutes in the same manner as in Example 2-1.

[0088] (Evaluation 2-1: Evaluation of Concentration Distribution of Epitaxial Wafer Using SIMS) As in Evaluation 1-1, the silicon wafer of Example 2-1 was subjected to magnetic field type SIMS measurement to measure the distribution of hydrogen concentration and carbon concentration in the thickness direction of the wafer. Figure 8 The concentration distribution of hydrogen and carbon in Example 2-1 is shown in FIG. Figure 6 (A) Similarly, regarding the depth on the horizontal axis, the surface of the epitaxial layer of the epitaxial wafer is set to zero.

[0089] (Evaluation 2-2: TO line strength evaluation by CL method) In the same manner as in Evaluation 1-2, CL spectra of the epitaxial wafers of Example 2-1 and Conventional Example 2-1 were obtained. Fig. 9 The results are shown in .

[0090] When compared Figure 6 (A) and Figure 8 When the peak concentration of hydrogen in Example 1-1 is about 2×10 18 Atom / cm 3 The peak concentration of hydrogen in Example 2-1 was reduced to about 3×10 17 Atom / cm 3 In addition, according to Fig. 9 It is known that in Example 2-1, at a depth of about 7 μm from the surface of the epitaxial layer ( Figure 7The peak of the TO line intensity is maintained at the same position as the peak of the TO line intensity in the other regions and has the same degree of TO line intensity as that of the previous example 2-1. Therefore, the epitaxial wafer that meets the conditions of the present invention can be said to have an epitaxial layer with a higher comprehensive crystallinity than before.

[0091] The reason for such a change in the TO line intensity is presumed to be that in the epitaxial wafer in which hydrogen is observed after epitaxial growth, hydrogen passivates the point defects contained in the epitaxial layer. On the other hand, in Comparative Example 1-1 in which the beam current value was set to 30 μA, no peak of the hydrogen concentration was observed, and therefore, it is presumed that no passivation effect by hydrogen was obtained in Comparative Example 1-1.

[0092] Industrial Applicability According to the present invention, a semiconductor epitaxial wafer having an epitaxial layer with higher crystallinity and a method for manufacturing the same can be provided. Such a semiconductor epitaxial wafer having an epitaxial layer formed thereon can improve the device characteristics of a semiconductor device manufactured using the semiconductor epitaxial wafer.

[0093] Description of Reference Numerals 10Semiconductor wafers 10A Surface of semiconductor wafer 16 Cluster Ions 18 Modified layer 20 epitaxial layer 100 semiconductor epitaxial wafers 200 semiconductor epitaxial wafers.

Claims

1. An epitaxial wafer comprising: a silicon wafer having a first surface; and An epitaxial layer on the first surface has a second surface, and the epitaxial layer has a TO line intensity distribution having a peak closer to the first surface than the second surface.

2. The epitaxial wafer according to claim 1, wherein: The TO line intensity distribution is characterized by a ratio of maximum intensity to minimum intensity of 8 or greater.

3. The epitaxial wafer according to claim 2, wherein: The ratio of the maximum intensity to the minimum intensity is 10 or greater.

4. The epitaxial wafer according to claim 1, wherein: The TO line intensity distribution is measured using cathodoluminescence (CL) spectroscopy.

5. The epitaxial wafer according to claim 1, wherein: The silicon wafer has a peak concentration of at least 1.0×10 17 Atom / cm 3 of hydrogen composition.

6. The epitaxial wafer according to claim 1, wherein: The silicon wafer has a peak concentration of 1.0×10 18 Atom / cm 3 and 1.0×10 22 Atom / cm 3 The hydrogen composition between them.

7. The epitaxial wafer according to claim 5, wherein: The peak concentration is located within 100 nm from a boundary between the silicon wafer and the epitaxial layer.

8. The epitaxial wafer according to claim 5, wherein: The peak concentration is located within 50 nm from a boundary between the silicon wafer and the epitaxial layer.

9. The epitaxial wafer according to claim 1, further comprising a modified layer in the silicon wafer, the modified layer being composed of at least carbon.

10. The epitaxial wafer according to claim 9, wherein: The carbon has a 19 Atom / cm 3 and 1.0×10 21 Atom / cm 3 The second peak concentration between 11. The epitaxial wafer according to claim 10, wherein: The second peak concentration is located within 150 nm from a boundary between the silicon wafer and the epitaxial layer.

12. The epitaxial wafer according to claim 11, wherein: The carbon concentration distribution has a half-height width in the range of 10 to 85 nm.

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